JPC SYSTEMIC PATHOLOGY
Signalment (JPC #2839300): 5-month-old male castrated crossbred Sus scrofa (domestic swine)
HISTORY: This animal was one of two affected in a group of 1000.
HISTOPATHOLOGIC DESCRIPTION: Haired skin and subcutis: Multifocally, in the dermis and subcutis there is necrotizing vasculitis with transmural infiltration of vessel walls by moderate numbers of neutrophils, fewer macrophages and eosinophils, eosinophilic cellular and karyorrhectic debris, hemorrhage, and fibrin. The inflammatory infiltrate and fibrin often extend into the surrounding dermis and subcutis. There is perivascular and periadnexal edema. There are overlying epidermal infarcts characterized by keratinocytes within all layers that have retention of cellular architecture but loss of differential staining and pyknotic nuclei (coagulative necrosis). Hair follicles in affected areas are similarly necrotic. In the less affected epidermis, there is mild epidermal hyperplasia and mild orthokeratotic hyperkeratosis with anastomosing rete ridges. Apocrine glands are moderately ectatic.
Kidney: Diffusely, there is segmental to global necrotizing glomerulitis characterized by disruption of glomerular tufts and replacement by numerous viable and degenerate neutrophils, necrotic debris, and abundant fibrin that extend into and fill Bowman's space; there are frequent fibrin thrombi within glomerular capillaries. Occasionally, there is periglomerular hemorrhage and multifocally the parietal and visceral epithelium of Bowman’s capsule is fused (synechia). There is necrotizing vasculitis of the arcuate vessels with hemorrhage, fibrin, and mild perivascular edema. Neutrophils, lymphocytes and macrophages expand the interstitium, separate and surround tubules. Multifocally, tubules are mildly ectatic and are often lined by attenuated epithelium and occasionally filled with an eosinophilic homogenous fluid (proteinosis), cellular debris (cellular casts), or rarely, degenerate neutrophils. Tubular epithelial cells are swollen and contain numerous, variably sized amphophilic vacuoles (degeneration).
MORPHOLOGIC DIAGNOSES: 1. Haired skin and subcutis: Vasculitis, necrotizing, neutrophilic, acute, multifocal, severe, with epidermal infarcts, crossbred swine, porcine. 2. Kidney: Glomerulitis and vasculitis, fibrinonecrotizing, neutrophilic, acute, diffuse, severe with fibrin thrombi, tubular degeneration, proteinosis, and cellular casts.
CONDITION: Porcine dermatitis and nephropathy syndrome (PDNS)
- Characterized by necrotizing and neutrophilic vasculitis in skin and kidney
- Type III hypersensitivity reaction
- Often associated with porcine circovirus 2 (PCV2); however experimental induction of PDNS with PCV2 inoculation has not been successful and PDNS has been induced in the absence of PCV2
- Other organisms which have been associated with PDNS in the literature include: PRRSV, Torque teno virus (arterivirus), Staphylococcus hyicus, Pasteurella multocida and Streptococcus suis
- PDNS is thought to be Type III hypersensitivity (deposition of immune complex in vessel walls)
- Vasculitis is primary lesion
- Immune complex deposits contain IgM, IgA, complement factor C3 and C1q
- Mechanism by which viruses trigger vasculitis
- Direct damage by invasion of endothelial cells
- Indirect damage through immune mechanisms in genetically susceptible individuals with some level of immune dysregulation
TYPICAL CLINICAL FINDINGS:
- Sporadic presentation and low prevalence (<1%) in affected herds; often fatal
- Skin lesions associated with necrotizing vasculitis
- Symptoms may also include anorexia, depression, stiff gait, often no pyrexia, and dyspnea
- Limb and periorbital edema often present
TYPICAL GROSS FINDINGS:
- Skin: Irregular red to purple, often crusted papules over hindquarters, perineal area, and ears
- Kidneys: Bilaterally enlarged, edematous, and pale with petechial hemorrhages
- Lungs: Noncollapsing and mottled with a suppurative bronchopneumonia
- Lymph nodes: Enlarged and dark red
- Heart: Most prominent lesion in infected fetus
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Necrotizing and neutrophilic vasculitis of dermis and subcutis
- Glomerulonephritis with thrombosis and infarction of adjacent tissue
- Also can see vascular lesions in spleen and mesentery
ADDITIONAL DIAGNOSTIC TESTS:
- Clinical signs are strongly suggestive but not pathognomonic
- Diagnosis made on the basis of gross and microscopic post mortem examination
- Vasculitis in swine
- PRRSV, African swine fever virus, CSF, BVDV, ovine herpesvirus 2, pseudorabies virus, Salmonella choleraesuis, Streptococcus suis, Erysipelothrix rhusiopathiae
- Necrotizing vasculopathy in swine
- Edema disease & cerebrospinal angiopathy by shiga-like toxins from coli, vitamin E and selenium deficiency
- Cutaneous and renal glomerular vasculopathy (Greenetrack disease/Alabama rot): Characterized by thrombosis, fibrinoid necrosis and leukocytoclastic vasculitis of cutaneous and cortical renal arterioles and glomerular capillaries occurring in greyhounds
- Gross TL, Ihrke PJ, Walder EJ, Affolter VK. Skin Diseases of the Dog and Cat. 2nd ed. Ames,IA: Blackwell Science; 2005:251-252.
- Krakowka S, Hartunian C, Hamberg A, et. al. Evaluation of induction of porcine dermatitis and nephropathy syndrome in gnotobiotic pigs with negative results for porcine circovirus type 2. Am J Vet Res. 2008;69(12):1615-1622.
- Langohr IM, Stevenson GW, Nelson EA et. al. Vascular lesions in pigs experimentally infected with porcine circovirus type 2 serogroup B. Vet Pathol. 2010;47(1):140-147.
- Robinson WF, Robinson NA. Cardiovascular System. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 3. 6th ed. Philadelphia, Pennsylvania: Elsevier; 2015:(3)69-70
- Opriessnig T, Meng XJ, Halbur PG. Porcine circovirus type 2 associated disease: Update on current terminology, clinical manifestations, pathogenesis, diagnosis, and intervention strategies. J Vet Diagn Invest. 2007;19:591-615.
- Opriessnig T, Langohr I. Current state of knowledge on porcine circovirus type 2-associated lesions. Vet Pathol. 2013;50(1):23-38.
- Rotermund A, Peters M, Hewicker-Trautwein M, Nolte I. Cutaneous and renal glomerular vasculopathy in a great dane resembling ‘Alabama rot’ of greyhounds. Vet Rec. 2002;151:510-512.
- Segalés J, Allan GM, Domingo M. Porcine circovirus diseases. In: Zimmerman JJ, Karriker LA, Ramirez A, Schwartz KJ, Stevenson GW, eds. Diseases of Swine. 10th ed. Ames, IA: Blackwell Publishing; 2012:262-263